Coned disc spring

ABSTRACT

A coned disc spring is arranged between a second component and a third component provided inside a tubular first component and movable in an axial direction. The coned disc spring comprises a body having a circular dish shape, teeth closely fitting into spline grooves formed on an inner peripheral surface of the first component and projecting to a radial outer side on an outer periphery of the body, and a stress relaxation portion formed in a flat shape or a curved shape at an edge portion of a circular arc portion at the base of the tooth in a direction at least one of a circumferential direction and a radial direction of the body.

TECHNICAL FIELD

The present invention relates to coned disc springs that are used toabsorb shocks occurring during the engaging of a clutch of a multiplateclutch structure of a transporting machine. Specifically, the presentinvention relates to improvement in a coned disc spring comprising teethfor inhibiting relative rotation with respect to a clutch drum.

BACKGROUND ART

A wet-type multiplate clutch structure is used as a clutch structure ina transmission of a transporting machine. The wet-type multiplate clutchstructure comprises a coned disc spring used for absorbing shocksoccurring during the engaging of a clutch. FIG. 3 is an enlargedsectional side view showing a composition of a multiplate clutchstructure 100 provided with a conventional coned disc spring 200. Themultiplate clutch structure 100 comprises a cylindrical clutch drum 101having a bottom. Plural spline grooves 101A extending in the axialdirection are formed on the inner peripheral surface of the clutch drum101 along the circumferential direction. In the clutch drum 101, atubular clutch hub 102 is provided thereto and has the common rotationaxis with respect to the clutch drum 101. Plural spline grooves 102Aextending in the axial direction are formed on the outer peripheralsurface of the clutch hub 102 along the circumferential direction.

Driven plates 103 and driving plates 104 are alternately arranged atpredetermined spaces between the clutch drum 101 and the clutch hub 102.The driven plate 103 is closely fitted to the spline groove 101A of theclutch drum 101, and the driving plate 104 is closely fitted to thespline groove 102A of the clutch hub 102, and they can move in the axialdirection. A piston 105, which is movable in the axial direction, isprovided at the bottom side of the clutch drum 101. An oil pressurespace 106 is provided between the piston 105 and the clutch drum 101.

A coned disc spring 200 having a hole in the center and a circular dishshape is provided between the driven plate 103, which is on the bottomside of the clutch drum 101, and the piston 105. The coned disc spring200 is supported by the driven plate 103 at the surface of the outerperiphery, and by the piston 105 at the back of the inner periphery.

In the above multiplate clutch structure 100, when operating oil issupplied to the oil pressure space 106, the piston 105 driven by oilpressure presses the driven plate 103, which is on the bottom side ofthe clutch drum 101, through the coned disc spring 200. Then, the drivenplate 103 on the bottom side of the clutch drum 101 moves to the openingof the clutch drum 101, and friction surfaces of the driven plate 103and the driving plate 104 which are placed oppositely to each other,engage, whereby they are clutched. In this case, the coned disc spring200 elastically deforms from the dish shape to become flattened, therebyabsorbing shocks that occur during the engaging of the clutch.

The above coned disc spring 200 has a circular shape, whereby it tendsto relatively rotate with respect to the clutch drum 101 during rotationof the clutch structure 100. Therefore, the coned disc spring 200frequently hits the inside wall of the clutch drum 101, which may causea problem of wear on the inside of the wall of the clutch drum 101.

In order to solve the above problem, a coned disc spring 300 has beenproposed (for example, see Japanese Unexamined Patent ApplicationPublications Nos. 2001-295860 and H9-329155). As shown in FIGS. 4A to4C, the coned disc spring 300 comprises a body 310 having a hole 310A inthe center and a circular dish shape, and plural teeth 311 are formed onthe outer periphery of the body 310. The body 310 of the coned discspring 300 is arranged at the inside of the clutch drum 101, so that theteeth 311 are closely fitted into the spline grooves 101A on the innerperipheral surface of the clutch drum 101, whereby the coned disc spring300 does not relatively rotate as described above.

When the above coned disc spring 300 is elastically deformed during theengaging of a clutch, a concentration of stress occurs at the base ofthe teeth 311. Therefore, there has been a problem in that thedurability of the coned disc spring 300 is greatly decreased.

In order to reduce the stress occurred at the base of the teeth 311, aradius of curvature R of a circular arc portion 311A at the base of theteeth 311 may be enlarged. In this case, the circular arc portion 311Aat the base of the teeth 311 extends in the circumferential directionand projects to the radial outer side. Therefore, if a corner portion ofthe spline groove 101A of the clutch drum 101 is sharp, the base of thetooth 311 heavily interfere with the spline groove 101A during rotationof the clutch drum 101. Accordingly, wear of the spline groove 101Acaused by the tooth 311 increases. Moreover, a length L of a straightportion 311B on the side of the tooth 311 is shortened, and the area inwhich the tooth 311 and the spline groove 101A are closely fitted isdecreased. Therefore, a contact pressure due to the tooth 311 at thespline groove 101A is increased, and the wear of the spline groove 101Acaused by the tooth 311 is increased. Specifically, in order to ensurethat the display of the correct mileage of an automobile, which has beenincreasing recently, the coned disc spring 300 is required to be highlydurable. Accordingly, the above problems need to be solved.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a coned disc spring bywhich stress occurred at a base of a tooth during the engaging of aclutch is decreased, and by which wear of a spline groove caused by thetooth is decreased.

The present invention provides a coned disc spring arranged between asecond and a third component provided inside a tubular first componentand which is movable in an axial direction. The coned disc springcomprises a body having a circular dish shape, teeth, and a stressrelaxation portion. The tooth closely fits into a spline groove formedon an inner peripheral surface of the first component, and it projectstoward a radial outer side on an outer periphery of the body. The stressrelaxation portion is formed in a flat shape or a curved shape at anedge portion of a circular arc portion at the base of the tooth in adirection of at least one of a circumferential direction and a radialdirection.

The coned disc spring of the present invention comprises a stressrelaxation portion formed in a flat shape or a curved shape at the edgeportion of the circular arc portion at the base of the tooth in adirection of at least one of a circumferential direction and a radialdirection. Therefore, when the above coned disc spring is arrangedbetween a driven plate and a piston in a clutch structure of atransporting machine, the stress relaxation portion can disperse andreduce stress occurring at the base of the tooth during the engaging ofthe clutch. Accordingly, stress occurring at the base of the toothduring the engaging of the clutch may be reduced. Moreover, even if acorner portion of a spline groove of a clutch drum is sharp, the base ofthe tooth does not project to the radial outer side, whereby it does notinterfere with the spline groove during rotation of the clutch drum.Therefore, wear of the spline groove caused by the tooth can be reduced.Furthermore, the straight portion on the side of the tooth is long,whereby the area in which the tooth and the spline groove are closelyfitted is large, and contact pressure due to the tooth at the splinegroove may be decreased. Therefore, wear of the spline groove caused bythe tooth during rotation of the clutch drum is largely reduced.Accordingly, the coned disc spring may have a high durability, therebyensuring proper display of recently increasing automobile mileage.

The coned disc spring of the present invention comprises a stressrelaxation portion at the base of the tooth. For example, when it isarranged between a driven plate (a second component) and a piston (athird component) at the inside of a clutch drum (a first component) of aclutch structure, the stress relaxation portion can reduce stressoccurring at the base of the tooth during the engaging of the clutch.Moreover, even if a corner portion of the spline groove of the clutchdrum is sharp, the base of the tooth does not interfere with the splinegroove during rotation of the clutch drum, whereby wear of the splinegroove caused by the tooth may be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1C are views showing a coned disc spring relating to thefirst embodiment of the present invention. FIG. 1A is a plan view, FIG.1B is a sectional side view taken along line B-B of FIG. 1A, and FIG. 1Cis a partially enlarged view of FIG. 1A.

FIGS. 2A and 2B are views showing a composition of a clutch structureprovided with a coned disc spring shown in FIGS. 1A to 1C. FIG. 2A is anenlarged sectional side view and FIG. 2B is an exploded view.

FIG. 3 is a sectional side view showing a composition of a multiplateclutch structure provided with a conventional coned disc spring.

FIGS. 4A to 4C are views showing a composition of another conventionalconed disc spring. FIG. 4A is a plan view, FIG. 4B is a sectional sideview taken on line B-B of FIG. 4A, and FIG. 4C is a partially enlargedview of FIG. 4A.

EXPLANATION OF REFERENCE NUMERALS

1 denotes a coned disc spring, 10 denotes a body, 11 denotes a tooth, 12denotes a stress relaxation portion, 12A denotes a circular arc portion,12B denotes a flat portion or a curved surface portion, 101 denotes aclutch drum (a first component), 103 denotes a driven plate (a secondcomponent), 101A denotes a spline groove (a groove), and 105 denotes apiston (a third component).

BEST MODE FOR CARRYING OUT THE INVENTION 1. Compositions of Embodiment

A. Coned Disc Spring

An embodiment of the present invention is explained with reference tothe drawings. FIGS. 1A to 1C are views showing a composition of a coneddisc spring 1 relating to a first embodiment of the present invention,and FIG. 1A is a plan view, FIG. 1B is a sectional side view taken alongline B-B of FIG. 1A, and FIG. 1C is a partially enlarged view of FIG.1A. The coned disc spring 1 comprises a body 10 having a circular dishshape and has a hole 10A having a circular shape in the center of thebody 10. The outer periphery of the body 10 is formed with plural teeth11 (for example, six teeth) at equal intervals along the circumferentialdirection. The teeth 11 have an approximately rectangular shape andproject to the radial outer side of the body 10.

For example, when the teeth 11 are applied to the following clutchstructure 100, they may prevent the coned disc spring 1 from relativerotating with respect to a clutch drum 101. It should be noted that theteeth used for the present invention are not limited to the teeth 11shown in FIG. 1, and various shapes of teeth may be used. For example,the teeth may have a shape which does not bend at the outer peripheralsurface of the body 10, and which extends along the outer peripheralsurface of the body 10. The number of the teeth was six, but this is notlimited thereto, and any number of teeth can be selected.

A stress relaxation portion 12 having a flat portion 12B is formed atthe base of the tooth 11. For example, the flat portion 12B is formed bycoining process in which an edge portion of a circular arc portion 12Aat the base of the tooth 11 is processed in a flat shape. For example,when the stress relaxation portion 12 is applied to the following clutchstructure 100, it reduces a concentration of stress occurring at thebase of the tooth 11 during the engaging of the clutch.

The coining process is performed at a predetermined position of aplate-like material for a spring before press working. In the pressworking, a hole 10A in the center and a tooth 11 of a body 10 are formedon the plate-like material for a spring. Instead of forming a flatportion 12B having a flat shape by the coining process, a curved surfaceportion 12B having a curved shape may be formed at the edge portion ofthe circular arc portion 12A at the base of the tooth 11 by coiningprocess.

B. Clutch Structure

The above coned disc spring 1 may be applied to a clutch structure 100shown in FIGS. 2A and 2B. FIGS. 2A and 2B show a composition of a clutchstructure 100, and FIG. 2A is an enlarged sectional side view and FIG.2B is an exploded view. A clutch hub 102 is omitted in FIG. 2B.

The clutch structure 100, for example, is a wet-type multiplate clutchstructure used for automatic cars. The clutch structure 100 comprises acylindrical clutch drum 101 (a first component) having a bottom. Pluralspline grooves 101A extending in the axial direction is formed on theinner peripheral surface of the clutch drum 101 along thecircumferential direction. In the clutch drum 101, a tubular clutch hub102 is provided thereto and has a common rotation axis with respect tothe clutch drum 101. Plural spline grooves 102A extending in the axialdirection is formed on the outer peripheral surface of the clutch hub102 at equal intervals along the circumferential direction.

A driven plate 103 (a second component) and a driving plate 104, whichhave a circular disc shape and are each formed with a hole in thecenter, are alternately arranged at predetermined intervals between theclutch drum 101 and the clutch hub 102. The driven plate 103 is formedwith plural teeth on the outer periphery thereof at equal intervalsalong the circumferential direction, and the teeth are closely fittedinto the spline grooves 101A. Therefore, the driven plate 103 cannotrelatively rotate with respect to the clutch drum 101, but it can movein the axial direction. The driving plate 104 is formed with pluralteeth on the inner periphery thereof at equal intervals along thecircumferential direction, and the teeth are closely fitted into thespline grooves 102A. Therefore, the driving plate 104 cannot relativelyrotate with respect to the clutch hub 102, but it can move in the axialdirection.

A piston 105 (a third component), which is movable in the axialdirection, is provided on the bottom side of the clutch drum 101. An oilpressure space 106, to which operating oil is supplied, is providedbetween the bottom of the clutch drum 101 and the piston 105. The piston105 is driven by the operating oil supplied to the oil pressure space106 in the axial direction. A return spring 107 is fixed by an endthereof on the surface of the piston 105 at the opening side of theclutch drum 101. The return spring 107 expands and contracts by pressureloaded thereon. The return spring 107 is fixed to a spring retainer 108by another end thereof. The return spring 107 biases the piston 105 tothe bottom of the clutch drum 101.

The above coned disc spring 1 is arranged between the driven plate 103,which is on the bottom side of the clutch drum 101, and the piston 105.In this case, in the coned disc spring 1, the teeth 11 are splined tothe spline grooves 101A, the body 10 is supported by the driven plate103 at the surface of the outer periphery thereof, and the body 10 issimultaneously supported by the piston 105 at the back of the innerperiphery thereof. Therefore, the coned disc spring 1 cannot relativelyrotate with respect to the clutch drum 101, but it can move in the axialdirection.

In the clutch drum 101, in order that the driven plate 103 and thedriving plate 104 do not move beyond a predetermined position, aretaining plate 109 is arranged at the opening side thereof. Theretaining plate 109 is formed with plural teeth on the outer peripherythereof at equal intervals along the circumferential direction, and theteeth are closely fitted to the spline groove 101A. Therefore, theretaining plate 109 cannot relatively rotate with respect to the clutchdrum 101, but it can move in the axial direction. A snap ring 110 isarranged on the surface of the retaining plate 109 at the opening sideof the clutch drum 101, so that the retaining plate 109 does not go offto the outside. The snap ring 110 is latched together with a ring grooveformed on an end of the opening side of the clutch drum 101.

2. Operation of Embodiment

The operation of the clutch structure 100 provided with the coned discspring 1 will be explained with reference to FIG. 2A.

When an operating oil is supplied to the oil pressure space 106, thepiston 105 is driven by the oil pressure, and it moves toward theopening side of the clutch drum 101 along the axis line with respect tothe bias power of the return spring 107. The piston 105 presses thedriven plate 103, which is on the bottom side of the clutch drum 101,through the coned disc spring 101. Then, the driven plate 103 and thedriving plate 104, which are alternately arranged, and the retainingplate 109 move to the opening side of the clutch drum 101 along the axisline. Thus, when the retaining plate 109 is pushed by the snap ring 110,the friction surfaces of the driven plate 103 and the driving plate 104which oppose each other, are engaged and are clutched. Therefore, torquecan be transmitted from the clutch drum 101 to the clutch hub 102.

In this case, the coned disc spring 1 is elastically deformed from thedish shape to become flattened, thereby absorbing shocks that occurduring the engaging of the clutch. When the coned disc spring 1 iselastically deformed, stress occurred at the base of the tooth 11 isreduced by the stress relaxation portion 12. The stress relaxationportion 12 does not project to the radial outer side, whereby the tooth11 does not interfere with the spline groove 101A during rotation of theclutch drum 101.

When the supply of the operating oil to the oil pressure space 106 isstopped, the piston 105 is pushed back to the bottom side of the clutchdrum 101 by the bias power of the return spring 107. Then, the frictionsurfaces of the driven plate 103 and the driving plate 104 aredisengaged and are unclutched, and the coned disc spring 1simultaneously returns to the former shape.

In the above first embodiment, the coned disc spring 1 comprises astress relaxation portion 12 formed by making the edge portion of thecircular arc portion 12 at the base of the tooth 11 in a flat shape or acurved shape in a direction at least one of a circumferential directionand a radial direction. Therefore, when the above coned disc spring 1 isarranged between the driven plate 103 and the piston 105 in the clutchstructure 100 of a transporting machine, the stress relaxation portion12 can reduce the stress occurring at the base of the tooth 11 duringthe engaging of the clutch. Furthermore, even if a corner portion of thespline groove 101A of the clutch drum 101 is sharp, the base of thetooth 11 does not project to the radial outer side, whereby it does notinterfere with the spline groove 101A during rotation of the clutch drum101. Therefore, wear of the spline groove 101A caused by the tooth 11may be reduced. The straight portion on the side of the tooth 11 islong, whereby the area in which the tooth 11 and the spline groove 101Aare closely fitted is large, and the contact pressure due to the tooth11 at the spline groove 101A may be decreased. Accordingly, the coneddisc spring 1 may have a high durability, thereby ensuring properdisplays of the recently increasing mileage of automobiles.

3. Additional Example

The present invention is explained with reference to the aboveembodiment, but this is not limited to the above embodiment, and variouscompositions are possible. For example, in the above embodiment, a coneddisc spring of the present invention is used for a wet-type multiplateclutch for automatic cars, but this is not limited thereto. For example,the coned disc spring of the present invention may be used for amultiplate clutch structure of a construction machine and a transportingmachine such as two-wheeled motor vehicles.

1. A coned disc spring, arranged between a second component and a thirdcomponent provided inside a tubular first component and movable in anaxial direction, comprising: a body having a circular dish shape; teethclosely fitting into spline grooves formed on an inner peripheralsurface of the first component and projecting to a radial outer side onan outer periphery of the body; and a stress relaxation portion having aflat portion formed in a flat shape or a curved surface portion formedin a curved shape at an edge portion of a circular arc portion at thebase of a tooth of the teeth, the edge portion being a boundary portionbetween the outer periphery of the body and a straight portion of thetooth, in a direction of at least one of a circumferential direction anda radial direction of the body.